In recent years, automobiles equipped with a plurality of lighted switch units in the front panels are increasing. Those lighted switch units may have push switches or rotary switches for easily controlling audio equipments, air-conditioners or other various electronic equipments.
A conventional lighted switch unit is explained using FIG. 5. The conventional lighted switch unit 501 includes operating body 1 made of insulating resin. Operating body 1 includes transparent or milky-white transparent part 1A; black or dark gray covering layer 1B formed by a painting method for instance in covering an entire outer surface of transparent part 1A; and light-transmitting display part 1C formed on an upper part of the operating body in exposing a part of transparent part 1A in a shape of letters and symbols.
Lighted switch unit 501 further includes case 2 made of insulating resin, and cover 3 made of insulating resin. In a middle part of case 2, cylindrical hollow part 2A is opened upward. Operating body 1 is placed movably in up and down directions and surrounds cylindrical hollow part 2A. Cover 3 covers an upper part of case 2. Operating body 1 extrudes upward from opening part 3A of an upper part of cover 3.
Printed wiring board 4 has a plurality of conductive patterns formed on an upper side and a bottom side of the board, and push switch 5 is mounted on the board. Depressing part 1D extends downward from an inside part of operating body 1 and contacts with operating part 5A of push switch 5.
On printed wiring board 4, electronic components including connector 6 (not illustrated) and light-emitting element 7, such as a light-emitting diode, are also mounted. Light-emitting element 7 is mounted near push switch 5.
Lighted switch unit 501 is installed in a front panel of automobile and is electrically connected to various electronic equipment including audio equipment and an air-conditioner as well as to an electronic circuit of automobile (not illustrated), through push switch 5 and light-emitting element 7.
When operating body 1 of lighted switch unit 501 is depressed, operating part 5A of push switch 5 is depressed by depressing part 1D electrically operating push switch 5; hence controlling audio volume and temperature of air-conditioner. When light-emitting element 7 emits light, an entire part of operating body 1 is lighted, illuminating light-transmitting display part 1C in a shape of letters and symbols. Thereby, a display of display part 1C and a position of operating body 1 are easily identified even in dark place or in night time. A similar illuminating switch is disclosed in Japanese Patent Unexamined Publication No. 2001-283673 for instance.
However, with the above conventional lighted switch unit, when light-emitting element 7 emits light illuminating the entire part of transparent part 1A which is at an inner surface of operating body 1, light transmitted to lower end 1E of transparent part 1A is reflected by case 2 leaking out through a gap between operating body 1 and opening part 3A of cover 3 as it is indicated by an arrow in FIG. 5. The leaked light makes the display of display part 1C hard to be seen. Thus, the device has a problem that the visibility of display part 1C is diminished.